Plural intermeshing feed or press screws



F. G. LESNIAK Sept. l1, 1951 5 Sheets-Sheet l Feb 12, 1945 Sept. 11, 1951 F, G, LESNlAK 2,567,2l9

PLURAL INTERMESHING FEED OR PRESS SCREWS Filed Feb. l2, 1945 5 Sheets-Sheet 2 WWWWW WMV I l I w Ill l ml l Ell l INVENTOR 5PM/K G- LefsA//nx ATTORNEY Sept 1l, 1951 F. G. LESNIAK 2,567,219

PLURAL INTERMESHING FEED OR PRESS SCREWS Filed Feb. 12, 1945 5 Sheets-Sheet 5 Ff?. e l ma ATTORNEY Sept. l1, 195i F. G. LEsNlAK 2,567,219

PLURL INTERMESHING FEED OR PRESS SCREWS Filed Feb. 12, 1945 5 sheets-sheet 4 asbl N INVENTOR FRANK 6- La'sN/AK ATTOR EY sept. 1.1, 1951 F; G', LESMAK' `2,567,219

PLURAL INTERMESHING FEED 'OR PRESS SCREWS Filed Feb. 12, 1945 5 Sheets-Sheet 5 Patented Sept. 11, 1951 PLURAL INTERMESHING FEED R. PRESS SCREWS Frank G. Lesnialr, Laurel, Miss., assignor to Masonite Corporation, Laurel, Miss., a corporation of Delaware Application February 12, 1945, Serial No. 577,378 Claims. (Cl. 100-48) This invention relates to improvements in conveying and pressing apparatus. It relates especially to such apparatus including intermeshing screws which are rotated in the same direction vand have. critical vrelationships of thread angles and dimensions that impart good meshing and fitting properties while permitting such rotation and the consequent opposite movement of the meshing parts of the respective screws.

Intermeshing screws turning in the same direction have heretofore been proposed, but with no disclosure or embodiment of the critical factors which I have found to be essential.

The apparatus in which the intermeshing screws are used must generally be designed in accordance with the use to which it is to be put. The embodiment shown in Fig. 1 is useful in c'onveying material eiliciently against high opposing pressure, as for example in feeding material against high steamvpressure as described in Patent No. 1,922,313 and issued August 15, 1933, to Mason. In a modified form, as shown in Fig. 2, the apparatus is useful in expressing liquid from liquid-containing material, as for example pressing liquid from fiber stock, or other vegetable and animal materials, and the like.

The invention has for an object the provision of intermeshing screws, which turn in the same direction and are so constructed that they mesh without binding or undue leakage, and the material being acted upon will be etliciently moved against opposing pressure by the rotation of the screws, with low power consumption and without the material turning with the screws. It is also an object of the invention to provide intermeshing screws to rotate in the same direction and having critical relationships of angles and dimensions'such that their respective meshing portions which move in opposite directions will neither bind by too close engagement nor provide openings detrimental to efficient conveyance of material by the rotary screws against opposing pressure. A further object is to provide an expressing apparatus including tapered intermeshing screws with increasing shaft diameter and decreasing outside thread diameter, whereby the volume of Athe space between successive threads decreases towards the outlet and increasing pressure is applied to the material through reduction of its volume. as it is moved toward the outlet.

vAdditional objects of the invention will be apparwith spiral threads which are suitable for conveying material against pressure.-

Fig. 2 is a plan view of tapered intermeshing screws adapted for expressing liquid from materials containing same.

Fig. 3 is a sectional view on line 3-3 of Fig. 2.

Fig. 4 is a partial plan view of one ofthe screws illustrated in Fig. 1.

Fig. 5 is a partial sectional view of the thread prof-lle on line 5-5 of Fig. 4.

Fig. 6 is a sectional. view of an apparatus embodying intermeshing screws adapted to convey materials against high pressure.-

Fig. 7 is a fragmentary sectional view of an apparatus including intermeshing screws and compression cones to remove liquid from material containing liquid. f-

Fig. 8 is a fragmentary sectional view of an apparatus embodying tapered intermeshing screws adapted to convey materials and simultaneously press the materials to remove liquid therefrom.

Fig. 9 is a view on line S-S fFig. 6 showing gear arrangement to drive the intermeshing screws in the same direction.

Fig. 10 is an end view of two intermeshing screws with a portion of one of the screws broken away.

Fig. 11 is a sectional view on section line I I-I l of Fig. 10, and showing the opposite inclinations of the intermeshing portions of the screw threads of the respective screws of a pair; and

Fig. 12 is a sectional view on section line iZ-IZ of Fig. 10.

With both screws of an intermeshing pair of like screws rotated in the same" direction, their respective parts in the intermediate meshing region move in opposite directions (see Figs. 3 and 10), and the portions of the threads 'which pass' one another in suchmovement are of opposite inclinations (see Figs. 11 and 12).

I have discovered that under these circumstances, proper meshing, Without binding or leaving openings detrimental to the forcing of materials against opposing pressure, can be attained only by having two critical relationships, one a relationship of angles and the other of dimensions.

Some of the screw dimensions are, of course, selected in accordance with performance requirements, volume of materials to be4 handled, rate of handling, nature and iinenessdegree viscosity, etc., of materials to be handled, pressure conditions which are to be met, and the like. These preliminarily-xed dimensions ordinarily include the outside diameter of the screw,v the diameter 3 at the root or base of the thread, and the pitch of the screw, designated D, d, and P respectively in the following table.

In Figs. 4 and 5, the parts and angles of the screw are designated as follows:

D is the outside diameter of the screw.

d is the root or shaft diameter of the screw.

P is the pitch or lead of the screw.

W is the width of the thread at its crest, that is,

at the outside diameter of the screw.

S is the distance between the threads at root diameter.

T is the depth of the thread.

Y is the angle of advance at root of thread, that is, the angle made by a tangent to the helix of the thread at root diameter with a plane perpendicular to the axis of the screw.

Z is the slant angle of the thread, that is, the angle made by the side of the thread with a plane perpendicular to the axis of the screw.

With d and P known, angle Y is determined by the following conventional equation:

The first of the critical relationships which I have discovered relates to angles and is that angle Z must exceed angle Y by at least minutes of arc, and may exceed angle Y to any greater extent than this so vlong as the ratio of width of screw threads at crest W to the distance between the threads at root diameter S is kept within limits hereinafter stated.

Tangent angle Y= This relationship may be expressed with symbols as follows:

Angle Z=angle Y plus at least 30 minutes With angle'Y determined as described above. an angle Z suitable for the purposes of the invention can be arrived at by addition of 30 minutes of arc or more to angle Y. The addition i of 30 minutes to about 60 minutes is ordinarily preferable.

The second of the two coexistent critical relationships which I have found essential relates to thread dimensions and is that the ratio of the width of the screw thread at the crest W to the distance between threads at the root diameter S shall be more than 55:100 and less than 65:'100, and preferably be approximately 60:100 or 3:5. This relationship can be expressed as follows:

W:S is over 55:100, under 65:100, and preferably about 60:100 or 3:5.

It is apparent from Figs. 4 and 5 that:

S|W=P2 tangent ZXT And since angle Z is now known, and may be, for example, angle Y+30 minutes, and T is obviously equal to Screws made to embody the above critical relationships will intermesh properly, and such intermeshing screws, when encased in suitable pressure resisting casings, as illustrated in the drawings, may be suitably used to convey materials against high opposing pressure or to press liquid from material containing liquid. The lntermeshing screws are rotated in the same direction to drive the material worked on forward. the material will not turn with the screws. and solid materials will not be wedged between the meshing portions of the threads because in the meshing region the parts of the respective screws move in opposite directions as indicated in Figs. 3 and 10.

As already stated, the respective portions of the intermeshing parts of the threads of a pair of intermeshing screws are oppositely inclined or slanted in the region in which they mesh with one another. This oppositely-slanting relationship is shown in Figs. 11 and 12. In said views the dotted lines 10W, which slant to the left, define the width W at crest of the threads o1' screw I0' of Fig. 10, and the lines IOS, which slant to the right, define the width S of the space between screw threads of screw I0". sections the intermeshing portions of the threads of screws I0' and I 0 through the middle, also shows how this slanting relationship is productive of relatively close engagement between the oppositely-moving, intermeshing thread portions of the respective screws l0' and I0", notwithstanding the thread-crest portions are narrower than the interspaces between the threads at root diameter, with a preferred ratio between their widths of 3:5.

The intermeshing screws may be rotated at any speed required for the material to be handled, and smooth and eflicient operation will be secured. If iiuid material, as for example oil, is being conveyed by the yintermeshing screws, speeds as high as 1800 R. P. M. or higher may be used. For continuously conveying wood chips into a gun against high pressure, as referred to above, lower speeds are desirable, as 100 R.. P. M. or lower.

The casings used to house the screws are prei'- erably made to iit closely within practical working tolerances to the outside contour of the intermeshing screws, which is substantially similar to the outline of the numeral 8, as shown in Fig. 3. Such close t is preferred between the casing and the exterior of the screws to avoid any substantially continuous openings in the apparatus which would lower the eiliciency in operation.

In Fig. 1, I have shown a plan view of a pair of intermeshing screws I0, I 0 formed integral with shafts l2 and operating within casing Il. These screws are made to embody the critical relationships described above and are adapted for conveying solid or fluid material against op# posing pressures. `The material is moved forward in spaces I5, l5 between the threads, such spaces being separated from one another at the region in which the threads of the two screws mesh together.

Use of such intermeshing screws in an apparatus made to convey materials against high pressure is illustrated in Fig. 6. In addition to the integrally-formed pressure screw sections I I, conventional, screw-conveyor flights vI8 are mounted on shafts I2 in the approximate area of the bottom of feed hopper I8. This feature e is desirable in order to feed a larger volume of material to the intermeshing screw sections Il Fig. 12, which `containers which the liquid has been pressed may be colvand thereby obtain greater volumetic eillciency in moving the material into the .region of high pressure, as for example'1000 p. spi. steam pressilre withinthe walls 20. `Screw shafts I2 are I, iinse-3landf32frespectively. Parallel shaftslZ,

. which .they interme'shing screws I0 are inte rn e rotated in the n same direction .Ofj bearing ,311.3

' jt. inte meshing;pressure'screws I0. Screws l0 i rotate .in these eachother-,wit

' e direction and intermesh' with i'itantially dense' pluguof material .'(to act as packst 'bearings 133 'suitable to take Collars'SQ-.are preferably pro- ;material; as *for example]A wood -K ed ntoivhopper i8', fand the screwf 'glits "l5 eed-the" material forward to but Vdecreases in depth on auniform taper toward substantiailyiittle `or no' slack` betweenthem,`andwil lconveythe material forf wai'd. into the regionof high" pressure; On startl 'ingupit is preferable thatuthefpressure within f the wallsj20 vbefbuilt 'up gradually. so that asub-` and outer surface of such modified form of screw are tapered in opposite directions, and the depth of thread is .greatest at the inlet end and decreases toward the outlet end fsothat-a compressing action is exerted on material moved along by the screws in the drection"ofarrow A of Fig. 2.

- Such vtapered screwswhich rotatev in the same direction andintermesh 'properly 'are preferably lconstructed asfo-llows; y

screw of uniform:outside-diameter'and with uniform d'epthof thread is firstiaid out in accordance with the critical relationships given abovelThena screw thread 52 is out ina c'y1in'" .jdrical blanlrof vthis outside diameter. This screw thread 52 is of; the. full depth of the layout at the right hand or inlet end,v as shown in Fig. 2,

the'left hand or -outlet end. The shaft portion 5U of the screw thus increases in diameter one. uniform taper toward the outlet end.

retains subsequently' the original diameter of the blankV at the inlet end and gradually decreases -j in -diameter'to the outlet end. Thus the outside of the screw is tapered at the same angle as, but

.juin-thegonposite directionfrom, the taper of the shaft portion 50.' ,In this way the cross section 1 of the space l5 between thread convolutions and move forward continuously.

The apparatus illustrated` in Fig s may be'v kmodified to convey material by'means 'of' intermeshing screws and at the same time'serve to 'press liquidfrom liquid-containing material. In

Fig. 7,'1' have showna fragmentary sectional view of such a modification wherein the forward end ofshaft I2 flares outwardly to form a. cone jl. 4Screws containing such modifications are preferablyplaced in casings containing openings move the material-forward against opposing pres-V V sure without the material turning with the screws. Material moved forward into space Il from thel area of intermeshing screws I0 will be subjected to pressure due to the decreasing space between the outer walls o f cone 38 and the inner walls of casing 42. Liquid pressed from the .ofmaterial kfinallybuilt up,.whioh together vwith the material ipazke'd .behindLit in the interthreadopenings willzwith'stand at -least 1000 p..s. ,i..back' pressure.. By `causing` screwsy Illf to exert' agiori ward thrust pressure greater thanthe back pres-k sure, the compressed materialiwill 'be `causedjto vclose-fitting exterior casing 54 gradually decreases .Y from inlet end to outlet end. Consequently, when material isvfed into an apparatus comprising two suchl intermeshing screws as shown` in Fig. 2, and the screwsgare rotated in the same direction, and thev materialmo'ved bythe screws in the direction of arrow-l A on Fig. 2,'it will besub- -gliected to predetermined gradual compaction, and

liquid will-be 'forced out"'of;it toA be drained Y `through'the'l spaoedfopenings -56fin the wall of if A sniaI v such as'j'ust' Adesciibedand-shown in 2, and

e apparatus for expressionof liquid,

havlngza compaction ratio of about? :.1. may comprise' intermeshing screws yrotatingjin rthe same direction, with each screw having',v for example,

the following dimensions:-

Length ef screw; 9"! l Outside ldiameter atinlet end; 3f' Outside diameter at outlet end: A2.33"

` Taper of frusto-'conical outer surface: 2"-7 min? utes material will'iiow through openings 44 in casing l2 and be collected through funnel 4G in suitable (not shown). The material from is 'shown which is designed to press liquids from' material containing liquid. The shaft portions Diameter of shaft portion at outlet end: 1.66"

vTaper of shaft portion (opposite direction to just- ,named taper) 27 minutes Thread depth at inlet endzl" Thread depth at outlet end: .3 3"

Intermeshing tapered screws as illustrated in Fig. 2 are conveniently used in pressing apparatus shown in the fragmentary sectional view in Fig. 8. In such apparatus material containing liquid is fed to the pressing apparatus through hopper 40 and conventional screw-conveyor flights i6 mountedon shaft 50 will, upon rotation, move the material forward into the sections containing the intermeshing tapered screws. Since the depth of threads 52 decreases as the receiver portion 58 is approached, the material carried forward between the rotating intermeshing threads 52 will be subjected to pressure. The liquid pressed from the material will flow through casing openings 56 into funnel I6 and can be collected in suitable containers (not shown).

Ihe pulpy mass remaining after removal of liquid from the material is collected in receiver 58.

The apparatuses shown in Figs. 7 and 8 are especially suitable for use in extracting liquid from material in continuous operations with a, high degree of efciency. The intermeshing screws of the several figures rotate in the same direction and material moved forward by the screws will not rotate with the screws.

Further modifications can be made to contain intermeshing screws having the described critical relationships and will be embraced within-the scope of the invention.

I claim:

1. A pair of intermeshing screws, integrally formed on parallel shafts, housed in a casing having an interior shape substantially similar to the outer contour of the intermeshing screws, and said screws being adapted to rotate in the same direction and capable of conveying material against'high opposing pressures in the order of 1000 pounds per square inch without the conveyed materials rotating with the screws, said screws comprising threads having hat crests parallel to the shafts, the ratio of the Width of the thread at the crest thereof to the distance between the threads at the root diameter being over 55:100 and under 65:100, and the angle made by the sides of the threads with a. plane perpendicular to the axes of the screws being at least 30 minutes greater than the angles of the helices of the screws at the root diameter with a plane perpendicular to the axes of the screws.

2. An apparatus adapted for conveying material and capable of conveying material against high opposing pressures in the order of 1000 pounds per square inch which comprises a pair of lntermeshing screws, adapted to rotate in the same direction, integrally formed on parallel shafts, and housed within a casing having an interior shape substantially similar to the outer contour of the intermeshing screws, said screws comprising threads having at crests substantially parallel to the shafts, the ratio of the width 8 cludes enlarged cone-shaped portions on the parallel shafts adjacent to the intermeshing screws and housed within the screw casing, said screw casing having a multiplicity of openings extending through the walls thereof.

4. A pair of intermeshing screws adapted to rotate in the same direction, said screws comprising threads integrally formed on parallel shafts having increasing diameter, with the exterior diameter of the screws decreasing in the same direction that shaft diameter increases, and the angle made by the sides of the threads with a plane perpendicular to the axes of the 'screws being at least minutes greater than the angle made by the helices of the screws at the root diameter with a plane perpendicular to the axes of the screws.

5. An apparatus to convey material containing liquid and simultaneously press liquid therefrom, which comprises a pair of intermeshing screws adapted to rotate in the same direction and housed within a. perforated casing having an interior shape substantially similar to the outer contour of the intermeshing screws, said intermeshing screws comprising threads integrally f formed on parallel tapered shafts and with the of the thread at the crest thereof to the distance between the threads at root diameter being approximately 3:5, and the angle made by the sides exterior of the screw along the crests of the threads tapered at the same angle as the shafts but in the opposite direction to the taper of the shafts, and the angle made by the sides of the threads with a plane-perpendicular to the axes of the screws being at least 30 minutes greater than the angle made by the helices of the screws at the root diameter with a plane perpendicular to the axes of the screws. I

FRANK G. LESNIAK.

REFERENCES CITED The following references are of record in the ille of this patent:

UNITED STATES PATENTS Number Name Date 1,631,119 Collins June 7, 1927 1,737,090 Meyers Nov. 26, 1929 1,777,250 Blazer Sept. 30, 1930 2,119,162 Hartner May 31, 1938 2,173,414 Fulton Sept. 19, 1939 2,360,984 Schmitz, Jr. Oct. 24, 1944 FOREIGN PATENTS l Number Country Date 109,663 Great Britain Sept. 25, 1917 310,625 Italy Aug. 28, 1933 

